MaryK, a while back I made a change to the site to improve performance and it worked really well. Your post came soon after I had turned this thing off for a couple of hours, so I connected the performance improvement with the image toggling problem.
So now the performance improvement is still in place, but I am excluding popup images. I still need to figure out why these two things don't play nicely together, but at least in the meantime you get popups.